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Microbial cells secrete extracellular polymeric substances (EPS) to adhere to material surfaces, if they get in contact with solid materials such as metals. After phase equilibrium, microorganisms can adhere firmly to the metal surfaces causing metal dissolution and corrosion. Attachment and adhesion of microorganisms via EPS increase the possibility and the rate of metal corrosion. Many components of EPS are electrochemical and redox active, making them closely related to metal corrosion. Functional groups in EPS have specific adsorption ability, causing them to play a key role in biocorrosion. This review emphasizes EPS properties related to metal corrosion and protection and the underlying microbially influenced corrosion (MIC) mechanisms. Future perspectives regarding a comprehensive study of MIC mechanisms and green methodologies for corrosion protection are provided. CA extern

A novel strain of an iron- and sulfur-oxidizing bacterium was isolated from a natural biotope at Kashen copper ore (Martakert Province, Republic of Artsakh). The strain is able to grow and oxidize ferrous ions in the range of pH 1.4–2.6 with optimal pH 2.0. The optimal temperature for growth is 35°C. Acidithiobacillus sp. Ksh has shown the highest activity for pyrite oxidation among other strains. It also demonstrated high activity in oxidation for copper and copper-gold bearing ores (Armenia). The isolate Acidithiobacillus sp. Ksh was identified as Acidithiobacillus ferrooxidans based on phylogenetic and physiological studies. Comparative studies of EPS production by cells grown on ferrous ions or pyrite were carried out. The chemical composition of capsular and colloidal EPS produced by Acidithiobacillus (At.) ferrooxidans Ksh were revealed to be proteins and carbohydrates. Exosaccharide produced by At. ferrooxidans Ksh is present mainly as polysaccharide in contrast to Leptospirillum (L.) ferriphilum CC, which is oligosaccharide. The structural difference of colloidal particles of these polysaccharides was due to the degree of hydration of the saccharide molecules. OA Förderung 2020

Sulfobacillus and Leptospirillum occur frequently in leaching systems. Here we investigated the effects of cells of L. ferriphilum on biofilm formation and leaching performance by S. thermosulfidooxidans. The effects were caused by the presence of L. ferriphilum or an addition of pyrite leach liquor from L. ferriphilum. Data show that the number of attached S. thermosulfidooxidans on pyrite increases, if the pyrite had been pre-colonized by living biofilms of L. ferriphilum, while it decreases if the pre-colonized biofilms had been inactivated. Coaggregation between S. thermosulfidooxidans and L. ferriphilum occurs during the dual-species biofilm formation, but different effects on bioleaching were noted, if the preculture of L. ferriphilum had been different. If L. ferriphilum had been pre-colonized on a pyrite, significantly negative effect was shown. However, if the two species were simultaneously inoculated into a sterile leaching system, the bioleaching efficiency was better than that of a pure culture of S. thermosulfidooxidans. The effect might be related to a metabolic preference of S. thermosulfidooxidans. If S. thermosulfidooxidans performed leaching in a filtered pyrite leachate from L. ferriphilum, the cells preferred to oxidize RISCs instead of ferrous ion and the number of attached cells decreased compared with the control. This study gives an indication that in a short-term multi-species leaching system the role of S. thermosufidooxidans may be related to the time of its introduction. OA Förderung 2020

Biooxidation of reduced inorganic sulfur compounds (RISCs) by thermoacidophiles is of particular interest for the biomining industry and for environmental issues, e.g., formation of acid mine drainage (AMD). Up to now, interfacial interactions of acidophiles with elemental sulfur as well as the mechanisms of sulfur oxidation by acidophiles, especially thermoacidophiles, are not yet fully clear. This work focused on how a crenarchaeal isolate Acidianus sp. DSM 29099 interacts with elemental sulfur. Analysis by Confocal laser scanning microscopy (CLSM) and Atomic force microscopy (AFM) in combination with Epifluorescence microscopy (EFM) shows that biofilms on elemental sulfur are characterized by single colonies and a monolayer in first stage and later on 3-D structures with a diameter of up to 100 μm. The analysis of extracellular polymeric substances (EPS) by a non-destructive lectin approach (fluorescence lectin-barcoding analysis) using several fluorochromes shows that intial attachment was featured by footprints rich in biofilm cells that were embedded in an EPS matrix consisting of various glycoconjugates. Wet chemistry data indicate that carbohydrates, proteins, lipids and uronic acids are the main components. Attenuated reflectance (ATR)-Fourier transformation infrared spectroscopy (FTIR) and high-performance anion exchange chromatography with pulsed amperometric detection (HPAE-PAD) indicate glucose and mannose as the main monosaccharides in EPS polysaccharides. EPS composition as well as sugar types in EPS vary according to substrate (sulfur or tetrathionate) and lifestyle (biofilms and planktonic cells). This study provides information on the building blocks/make up as well as dynamics of biofilms of thermoacidophilic archaea in extremely acidic environments. OA Förderung 2019

Dissertation, Universität Duisburg-Essen, 2015 In this study, biofilm formation and extracellular polymeric substances (EPS) of acidophilic archaea were investigated. Three representative archaeal species extremely acidophilic archaeon Ferroplasma acidiphilum, thermoacidophilic archaea Acidianus sp. DSM 29099 and Sulfolobus metallicus were chosen as test organisms. Several cultivation and advanced microscopical techniques e.g. CLSM, AFM & EFM and SEM were used to visualize and characterize biofilm development and EPS of acidophilic archaea. In addition, FLBA, ATR-FTIR and conventional spectroscopic methods were applied for qualification and quantification of EPS components. F. acidiphilum biofilms were heterogeneously distributed on polycarbonate filters over time, and varied within the different growth conditions such as supplementation with glucose. Cells formed a monolayer biofilm and were preferably attached to the defect sites of pyrite surfaces. Biofilm and planktonic cells exhibited significant morphological differences as revealed by AFM. Low coverage of pyrite surface by cells seems to correlate with their low leaching ability. Screening of a lectin library resulted in the detection of 21 lectins able to bind archaeal biofilms on pyrite and to Acidianus sp. DSM 29099 biofilms on elemental sulfur (S0). These lectins can be used in studies for assessment of interactions between various members of microbial bioleaching communities, especially in order to elucidate the role of archaea in detail. The major binding patterns, e.g. tightly bound EPS and loosely bound EPS, were detected on both substrates pyrite and S¬0. The three archaeal species produced various EPS glycoconjugates containing sugar moieties like glucose, galactose, mannose, GlcNAc, GalNAc, sialic acid, and fucose. Additionally, the substratum induced different EPS glycoconjugates and biofilm structures for cells of Acidianus sp. DSM 29099. EPS analysis of S. metallicusT on S0 showed that capsular EPS from planktonic cells were mainly composed of carbohydrates and proteins. In contrast, colloidal EPS from planktonic cells were dominated by carbohydrates. Proteins were found to be major components in EPS from biofilms on S0. In addition, extracellular proteins and nucleic acids were present in the EPS matrix. The existence of these compounds suggest their potential roles in biofilm formation and stabilization. S. metallicusT cells were shown to be embedded in a gel-like and flexible EPS matrix, where cells were often found to be motile (back and forth) either self-propelled by cellular appendages or by ‘Brownian motion’.